DIY Custom Molded Earbud Roundup

Headphones have become ubiquitous these days. Thanks to the iPod and the smartphone, it’s become commonplace to see someone wearing a pair of earbud style headphones. Earbuds aren’t always comfortable though. On some people they are too loose. On others, the fit is so tight that they cause pain.To that end, we’ve found a few great solutions for this problem.

[cptnpiccard] has documented his custom molded Sugru earbuds in an Imgur gallery. He’s molded a pair of standard earbuds into a cast of his ear. He uses them both for hearing protection and tunes while skydiving. Sugru’s FAQ states that while the cured material is safe for skin contact (and in ear use) some people are sensitive to the uncured material.

While discussing his project on Reddit, a few users chimed in and mentioned they’ve made custom molded earbuds using Radians custom earplug kits. The Radians material hardens up in only 10 minutes, which beats waiting an hour for Sugru.

The absolute top of the food chain has to be building your own triple driver in ear monitors, which is exactly what [marozie] has done. Professional custom molded monitors can cost over $1000, which puts them in the realm of professional musicians and audiophiles. [marozie] discovered that mouser stocks quite a few transducers from Knowles. These tiny speakers don’t come cheap, though; you can spend upwards of $70 just for a single driver.

[marozie] took a cast of his ear using an earmold impression kit. He used this cast to create a mold. From there it was a matter of pouring resin over his carefully constructed driver circuits and audio tubes. The resulting monitors look and sound incredible.

It goes without saying that making custom in ear monitors involves putting chemicals into you ears. The custom earmold kits come with tiny dams to keep the mold material from going in too far and causing damage. This is one of those few places where we recommend following the instructions. Click past the break to see a demo video of the ear molding process.

You might be misreading the silent video! If you make those shapes with your face, it’s a good way to open your Eustachian tube, which equalises the pressure as the plug is withdrawn. You can do the same thing while taking off/landing in a plane, or chew on a sweet for the same effect. I would guess she was intentionally doing that rather than grimacing in pain.

What in the actual fuck… I mean, I don’t care what people like to do sexually in private (as long as it doesn’t harm someone else), but really… what the fuck. How does the thought even enter your head to do something like that?

I have no personal knowledge of this case but I imagine it going like this:

I have a poor understanding of the alkalinity of concrete or rectal foreign bodies or how bad of an idea this is but I wish to engage in behavior that will somehow create a perfect mold of my rectum because that “makes perfect sense” and concrete hardens so grab the funnel and let’s get’r’done? Hold my beer?

I can’t imagine this was some kind of concrete construction worker roleplay gone bad.

Can anybody confirm that Reoflex is free of organomercury salts, such as phenylmercuric neodecanoate? Organomercury salts are excellent, highly selective catalysts for polyurethanes but, well, they are made of mercury salts. Not exactly something you want to put in your ear or use to cast something you will be putting in your ear.

Are you serious? I would highly recommend modifying the procedure to use less toxic materials.

First of all, Sugru isn’t quite as non-toxic as they’d like to claim. There are only a few types of moisture cure (in other words, “air dry,” one part) silicones: those which release alcohols during cure (ethyl or methyl, typically), or those that release acetic acid. Given that sugru doesn’t smell like vinegar, it’s probably the former. Unfortunately, the latter will typically have some tin-based catalyst, which is slightly toxic. I would seriously not want to put that in my ear canal. Checking the MSDS, sugru does indeed have some slightly toxic tin-based catalyst in it. Additionally, it takes a heck of a lot longer to cure and will probably evolve some alcohol. If you want to put something in your ear that’s actually reasonably safe (and actually cures faster, given that it’s not thickness-dependent), I’d get some platinum-cure silicone moldmaking putty. Many of these are in fact food grade when cured, so it’d be relatively safe. Michael’s and most crafts store have them; they are two part, but considerably faster curing and safer on your ear (half hour, and at body temperatures, probably faster than that). If you like Smooth-On, you can try their Equinox series. GT silicones has a nice series as well.

One warning though: Food grade after cure is not a guarantee of safety during application. There are a few silicones that manufacturers will recommend for lifecasting, but the only one that’s technically been approved as safe for skin contact is Smooth-on’s Body Double. Unfortunately it’s not quite the right rheology and a thixotropic liquid rather than something more like clay. If you’re really adventurous, you can make it correct by spending some time kneading A and B with a bit of fumed silica (enough of other mineral fillers may work as well; I’d use a ton of baby powder if I were concerned about skin safety)

The material used for molding is also just a really bad idea. First of all, Smooth-on really isn’t the best choice for polyurethane rubbers. As a previous poster said, many casting companies have not gotten around to switching away from older rubber formulations, and still use toxic mercury-based catalysts. You really do not want this near your skin. Luckily, Reoflex is one of the few in their product line that is not, but having worked with enough polyurethane elastomers (check their MSDS), you probably do not want any of the residual amine catalyst to be in contact with your skin or any of the phthalate plasticizers in this PU formulation to be in contact with your skin. I’d recommend casting the actual earplug out of some platinum cure silicone elastomer. If it’s food grade, it’s likely okay for your skin, and Smooth-on (and most other suppliers–Quantum Silicones comes to mind, along with the EasyMold stuff at Michael’s) makes plenty that are okay for that. Mold release is a bit more of a pain-in-the-arse because silicone likes to stick to silicone, but a few thou off because you used petroleum jelly isn’t the worst thing in the world. Many silicone earplugs are already made of silicone. I will say, though, that standard silicone formulations tend to have very high coefficients of friction, and having not gotten around to casting my own earbuds, I can’t say I know if that’s a problem. There are obviously additives that help in this department.

Alternatively, if you’re insistent on using polyurethane, there are a few medical grade polyurethanes sold by Hapco, but they are much more difficult for someone who doesn’t have a lot of casting equipment to mold with. These are more or less plasticizer free (or have some safe plasticizer). It is exceptionally difficult to find polyurethane casting elastomers that don’t have some nasty plasticizer or catalyst; most of them smell quite strongly after demold, and many will not rid themselves of the smell for many weeks (and in some cases, if they do and the plasticizer is lost, well, you also lose the flexibility of the part. Basically, IF YOU ARE DOING THIS WITH POLYURETHANE ELASTOMERS, CHECK THE MSDS AND MAKE SURE THE RESIN YOU ARE USING IS SAFE. BE ESPECIALLY ON THE LOOKOUT FOR MERCURY CATALYSTS. A good point of reference is Michal Zalewski’s “Guerrilla guide to CNC machining, mold making, and resin casting,” which says a lot about casting chemistries and what to look for as a hobbyists. The guide’s been posted on Hackaday at least a few times.

What other ones are there? I’d really like to know. I’ve certainly heard of a few companies which advertise skin safe silicones (Silpak Silputty, maybe something by platsil??, and something by Artmolds), but none of them have an ACMI approval label, and I vaguely remember Smooth-on once claimed they were the only lifecasting silicone with the ACMI label. Totally separate issue, I remember reading an article once that there’s some politics behind getting yourself an ACMI label (potentially releasing formulas to competitors, etc.) and I’d imagine a lot of smaller companies just don’t want to pay the fee, so I wouldn’t be surprised if these other brands were fine. But do you know of any other ACMI skin safe silicones? (okay, well, obviously, I mean RTV silicones that are skin safe for the lifecasting processing, not skin safe after molding, which is obviously fairly easy to find) Body double is awfully expensive, and I’ve always assumed this was because they were the only ones who went through with the ACMI compliance testing

Better yet, don’t do this at all. It’s only $50 or $60 dollars to have a professional audiologist make impressions of your ears. Why risk your health when a professional can do it for relatively little cost? In fact, that’s how those $1000 earbuds get made. I went through the procedure a year ago for my musician’s earplugs/ue earbuds and it was fast and painless.

Looks like marozie beat me to it. He had an “allergic reaction” to Smooth-on crystal clear. It’s unlikely that it’s the isocyanate–that’s typically reactive enough that it’ll be gone before long (though some of the smooth-on stuff takes so long to set that if he didn’t wait long enough, it’s possible there was some free isocyanate), but the crystal clear series very, very, very definitely has a large amount of mercury catalyst in it (not ppm, but 0.25% in the cured product!) Should have noticed the huge warning label on the crystal clear resin that says “INDUSTRIAL USE ONLY!” Often times, there are also other plasticizers that might not be safe to put in the ear, but are not legally required to be added to the MSDS, so you never really know. If you don’t have much experience with casting and don’t mix well enough, that could also be out there. There are safer products out there, but it’s important to look carefully at the safety data sheets and really just look for products that are at least food grade or something similar before sticking cast parts in your ear. I should add that this is particularly true for clear /and/ elastomeric PU resins, as both have been traditionally more difficult to formulate without a mercury catalyst. Clears tend to require high vapor pressure isocyanates, which can be toxic /during casting/ even in extremely minute amounts (used to be a big problem in the automotive clear coat industry)

What makes you say that? The guide is not about 3D printing but the shortcomings mentioned there are still valid IMHO, unless you have access to very expensive commercial 3D printer of course. If you are talking about UV cure printers, they are not good for general purpose use due to very limited options for resins.

He’s not using speakers, but balanced armature drivers. There is actually a difference, each part is optimized to reproduce a certain range–balanced armatures actually have great difficulty with the lower end of the spectrum, so at leasthaving an armature dedicated to bass makes sense.

The issue with molding earphones this way is that you’re not getting optimal transducer positioning. Your ear canal engenders specific quarter-wave resonances that alter the way you perceive music as it’s reproduced. The whole point behind custom-molded in-ear monitors isn’t just for isolation (there are some universal-fit ones that do just as good or better of a job), but also that the drivers inserted into them, whether they’re dynamic or balanced armature transducers, are properly optimized for good sound quality.

The second issue (and perhaps the more pressing one) is that Sugru, while they’re “acceptable” for skin contact, have not been tested for long term contact, where skin oils, cerumen, and sweat can easily break down the polymer material, in addition to creating potential allergens. It also seems like porous material that easily promotes bacteria growth, leading to an environment that might lead to infection if you have an open wound (can be very small) on your ear. Most custom IEMs, whether they’re acrylic or silicone based, use a finishing lacquer with nano-treatment that helps prevent bacterial growth, as well as promoting easier cleaning.